91 Convertible Exhaust Suggestions (too Stinky)

koala33 · Mar 23, 2015

So this is my second Foxbody - the first was an 89, and I had just about the same setup exhaust-wise. I remember the 89 would leave me smelling like gas if I had the windows and or the top down. So me, not thinking, decided to do the same thing with my 91. I guess I just wasn't thinking.

I have stock headers, BBK Offroad X-Pipe, and American Thunder Flowmasters. Car is low mileage (38K), so I am assuming the headers are solid and have no leaks, but I have not physically checked. I decided to take off the catalytic converters when they put on my exhaust because I wanted a meaner sound. I screwed up by doing this and now I am trying to figure out the best course of action to make my car drivable again without me stinking like gas.

Should I try to find someone to put catalytic converters back on? Would this more than likely take away the odor? Keep in mind I sold them for a couple hundred bucks when I put on my exhaust, so I will have to find some more somewhere.

I think my first course of action will be to take my car back to the garage where they put everything on and have them check everything out underneath to see if there are any leaks?

Trying to get the car ready for spring, but the top can't go down until I get this fixed!

Thanks!!

Mustang5L5 · Mar 23, 2015

Converters would solve your issues.

I went through the same issue. Took mine off, hated the stench of raw fuel, put them back on and enjoy not smelling like a gas station.

Plus i like the quieter exhaust. As i've gotten older, excessively loud exhaust is starting to annoy me

mikestang63 · Mar 23, 2015

either out a catted h pipe or the cats back on with the smog pump and hoses

koala33 · Mar 23, 2015

So the smog pump and hoses are still on... When buying converters, do I have to buy converters specific for a 91 Mustang, specific to fit my BBK X-pipe, or are they general in size? I'm assuming that is going to be expensive - I shouldn't have sold them..

mikestang63 · Mar 23, 2015

If the smog pump, hoses, TAD and TAB sensors are still on, then it is simply a matter of reinstalling the catted mid pipe and hose from the catted H pipe bacl to the crossover tube fitting coming off the smog pump hoses. Hopefully the crossover tube is still attached to the back of each head. and is capped off on the hose.

Any fox body cat pipe- 87-93- will work. You can either get a used stock set or companies maike aftermarket performance catted H pipes..Used stock catted mid pipes sell for $50 for $100. Aftermarket ones $3-400

koala33 · Mar 23, 2015

That totally sucks - I wasted a few hundred on the X-Pipe. I guess you live and you learn. I can only assume everything is still where it needs to be. I am taking it to the shop where it was installed on Thursday, so I can ask him if simply adding a catted H pipe will work. Maybe I can turn around and sell the X-pipe on craigslist or something.

mikestang63 · Mar 23, 2015

Not that I would recommend this, but they also sell afterarket performance cats that you can weld into your aftermarket pipe. Just giving you options

koala33 · Mar 23, 2015

That's what I was wondering, but it seems for viable to just buy a new pipe altogether and have it put on. That way it is done right. May be time to throw in headers too while I'm at it.

mikestang63 · Mar 23, 2015

shorty headers are nice to look at and may give you some rumble, but they add nearly nothing in HP and on a stockish engine will result in lower low end torque.

Spend your money elsewhere IMO like a good cat back system.

koala33 · Mar 23, 2015

This may be a dumb question but I may just swap out myself rather than pay someone (here in the DC area) $150+. There are 4 O2 sensors right? If I buy a catted H-Pipe, which 2 O2 sensors get hooked up? Everything is bolt-on, so I am fairly certain with a lift I can swap out. Are there any gaskets where the headers/midpipe and midpipe/catbacks merry?

mikestang63 · Mar 23, 2015

koala33 said:
This may be a dumb question but I may just swap out myself rather than pay someone (here in the DC area) $150+. There are 4 O2 sensors right? If I buy a catted H-Pipe, which 2 O2 sensors get hooked up? Everything is bolt-on, so I am fairly certain with a lift I can swap out. Are there any gaskets where the headers/midpipe and midpipe/catbacks merry?

fox body cars have O2 sensors located upstream of the cats. Not a terribly hard job, you just need to jack the car high enough to be able to jostle the old and new pipes in. No gaskets as everything is either ball and socket or flange fit.

You will need

socket with long extensions with swivels
deep 1/2" socket
Plenty of penetrating spray
long amount of rubber fuel line and hose clamps to connect the air tube on the catted h pipe to the connection on the metal bung on the pasenger side of the motor
possible some new muffler/pipe clamps if the old ones are rusted
Disconnect the battery first as a precaution

Now sometimes you do need some exhaust gaskets between the stock header and H pipe flange it they are warped- normally you do not. Make sure that you tighten each side up a little at a time so not to cock it. You want the H pipe to be pulled on evenly. Support the rest of the exhaust when you disconnect the H pipe to make it easier to reinstall. It iis easier to place the H pipe on a long 2 x 4 and jack it up with the pipe resting on the board as support.

Since the shop just installed the new H pipe, chances are the header stud bolts will come off easy. I would spray them down liberally with PB blaster just in case. You do not want to snap a stud off or you will need to remove the header to install a new one. It is somewhat of a PITA to get the passenger nuts- you will need some long extensions and a swivel. Do not crank down on the header studs- torque them to specs. I think maybe 15-20 ft lbs off the top of my head. After you have the studs tightened down, tighten up the rear of the pipe to the exhaust same way- equal amounts.until all the gap is gone.

Test for leaks

koala33 · Mar 23, 2015

Great thanks for the write up, it is greatly appreciated.

Shawn

cobra10494 · Mar 23, 2015

If your going the catalytic route,go with some high flow cats..don't rob you of power and get rid of the awful smell.

elarm1 · Mar 23, 2015

Put some cats back on. You can try this place American High Performance Mustang Camaro Corvette Dodge Hemi but they will wring you dry. I have a Mustang exclusive guy in Manassas off of Euclid. I can get his info for you

90lxwhite · Mar 24, 2015

I had a 90lx w an off-road x and it stunk. Come inspection time I had to have cats anyway so I had a set of "high flows" welded in. It was a little quieter but no more stink.

Mustang5L5 · Mar 24, 2015

Only 2 O2 sensors on the fox.

Sell your Xpipe to help finance the catted pipe

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91 Convertible Exhaust Suggestions (too Stinky)

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